Anand,
First of all, IMAP Push uses more battery than regular mail checking, especially with Gmail, which "tickles" the app every 5 minutes even if nothing happened.
Second, if you're still interested in IMAP Push, please check the account's Options and Folders. Both the account's IMAP Push and at least one folder's IMAP Push should be enabled.
If the settings are correct, then you should have a status bar icon (a blue "@" sign) saying "Push mail: <account name here>".
If you see the status bar icon, please let me know by email (kmansoft / gmail), I might have other ideas.